I looked around the Jolla operating system and figured out that it should be possible to share the network connection through Bluetooth, specifically my laptop running OS X Mavericks.

Now, my first step was to simply start pand --listen --role NAP --master and see if the laptop would connect its Bluetooth PAN profile. I had to delete and reassociate the Jolla, only then was it shown as a PAN device (Mavericks no longer has a button to rescan the Bluetooth profile, although there may be a utility for the purpose in XCode).

Then I assigned a fixed IP address (private, off the top of my head, not in use anywhere in the nearby networks) to the Bt PAN interface on the laptop, after which its status changed to "Connected". What this means is something of a mystery, however, as there was no outward route from the laptop, and there was no obvious interface at either end to create it to.

(Of course I could just route 3G to WiFi with iptables, provided this thing knows how to make an ad-hoc network, but where's the fun in that? )

Helpful advice is welcome. If the Jolla 1/2014 update introduces a WiFi or Bluetooth sharing function, I'll be very happy indeed

The next step would be to find out how to get the two devices talking to each other over Bt, the rest is trivial

I was able to set up a PAN between my laptop and my Jolla phone only after uncommenting

DisablePlugins = network

in /etc/bluetooth/main.conf on the telephone, and then starting pand with the appropriate options on both sides (phone and laptop)

I can now ssh into the phone over the bluetooth link.

Of course bridging and dhcp would be the icing on the cake, but now that I have a connection I should be able to proceed in much the same way as with an USB link and use the phone as a gateway to the internet.

Once the connection was successful, since there was no DHCP server that I knew of, I just configured the interface manually:
ifconfig bnep0 address broadcast broadcast netmask netmask
ifconfig bnep0 up

At the Mac end I gave a static address, and voilą - I was tethered.

Of course these commands should be scripted and wrapped into a nice UI, and DHCP might be nice to reduce the need of configuration at the other end, but there's no technical obstacle to any of this.

I did not expect this to be solved so easily and quickly. Underneath its shiny user interface, the Jolla is a completely standard linux system, so with a little Googling, most of the 'sysadmin-like' problems (like this one) should be easily solvable.

Once the connection was successful, since there was no DHCP server that I knew of, I just configured the interface manually:
ifconfig bnep0 address broadcast broadcast netmask netmask
ifconfig bnep0 up

At the Mac end I gave a static address, and voilą - I was tethered.

Of course these commands should be scripted and wrapped into a nice UI, and DHCP might be nice to reduce the need of configuration at the other end, but there's no technical obstacle to any of this.

In fact, forget all the above. After a bit of research, I found the simplest solution.

pkcon install connman-test (you only need to do this once)

cd /usr/lib/connman/test; ./enable-tethering bluetooth

???

profit!

Conversely, if you want to stop tethering, just run
cd /usr/lib/connman/test; ./disable-tethering bluetooth

This does all that is needed for tethering. All that Jolla needs to do is put a nice friendly button on the UI

I did not expect this to be solved so easily and quickly. Underneath its shiny user interface, the Jolla is a completely standard linux system, so with a little Googling, most of the 'sysadmin-like' problems (like this one) should be easily solvable.

Yes, that's the nice bit about it. I've "grown up" around *nix systems since 1995 and done various sysadmin jobs for a living since 1997 (which is also how I fund my current studies in a completely different field), so I quite like the idea of carrying a Linux box in my pocket